1. Field of the Invention
The present invention relates to a transmission apparatus and related program provided with a failure determining method and function for, when a failure occurs in an information system including a transmission apparatus transmitting control information and a reception apparatus transmitting response information to the control information and the causal location is to be found out, narrowing down a range of the causal location to facilitate the cause investigation.
2. Description of the Related Art
Generally, an information system consisting of a server, a client, storage and others has a transmission apparatus transmitting control information and a reception apparatus transmitting response information to the control information. For example, Japanese Patent Application Laid-Open Publication No. 1993-40744 describes an information system with a host computer transmitting a response frame (response information) to a control frame (control information) transmitted by an I/O apparatus.
Also, from the view point of a model of the server-storage model, the server issues a read instruction (control information) and the storage responds to the read instruction with data (response information) stored in the storage. Also, the server issues a write instruction (control information) and the storage responds to the write information with a write completion notification (respond information).
Currently, when the information system is constructed, SAN (Storage Area Network) is increasingly constructed which connects the serve and the storage with high-speed network using the fiber channel, i.e. an interface standard for performing high-speed and long-distance data transfer. For Example, Japanese Patent Application Laid-Open Publication No. 2002-91708 discloses a disk array apparatus using a fiber channel interface (hereinafter, referred to as FC interface).
In these information systems, if the response information to the control information transmitted by a transmission apparatus cannot be obtained from the reception apparatus, the transmission detects a timeout error. The timeout error is often caused by a failure location occurring in any one of the transmission apparatus, the reception apparatus and communication path connecting the transmission apparatus and the reception apparatus.
However, in prior art, if a transmission apparatus detects a timeout error, it is difficult to identify a failure location causing the error. For example, if the timeout error occurs between a server and storage, the server cannot determine whether the cause of the error is: that the storage does not function, although the server has transmitted I/O instructions such as a read instruction and write instruction; that a communication path to the server has a problem, although the storage has transmitted the response information; or that an FC interface of the server is broken and the I/O instructions issued by the server has not been transmitted.
Therefore, if the timeout error between the server and the storage occurs on an end user's site where an information system was delivered, it takes time to identify the failure location. In other words, a long time is needed for recovering the information system to a normal state, and it is problematic that a significant impact is placed on end users using the information system for business purpose.